Caption: Floret (flower bud, apical meristem) of a broccoli head (Brassica oleracea italica), coloured scanning electron micrograph (SEM). Shown here is a small flower bud with actively dividing apical meristem tissue along the leading edges of the bud. Apical meristems are the completely undifferentiated (indeterminate) meristems in a plant. At the meristem summit there is a small group of slowly dividing cells which is commonly called the central zone. Cells of this zone have a stem cell function and are essential for meristem maintenance. A short distance from the apical meristem cells begin to differentiate and epidermal cells with stomata can be seen developing. Broccoli is one of several vegetables in the species Brassica oleracea, in the family Brassicaceae (Cabbage Family). Broccoli possesses numerous fleshy flower heads (usually green in colour) arranged in a tree-like fashion on branches growing from a thick stalk. Magnification: x20 when shortest